バイトコードアクション_JAvassistライブラリ_新しいクラスを動的に作成_属性_メソッド_コンストラクタ_API詳細JAVA 216-217

ソース:http://www.bjsxt.com/一、S 02 E 216_01バイトコードアクション_JAvassistライブラリ、紹介、動的新規クラスの作成、プロパティ、メソッド、コンストラクタ
バイトコード動作
一般的なバイトコード操作クラスライブラリ
JAVASSIstライブラリ

package com.test.javassist;

import javassist.CannotCompileException;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtConstructor;
import javassist.CtField;
import javassist.CtMethod;

/**
 *     javassist       
 */
public class Demo01 {
    public static void main(String[] args) throws CannotCompileException, Exception {
        ClassPool pool = ClassPool.getDefault();
        CtClass cc = pool.makeClass("com.test.bean.Emp");

        //    
        CtField f1 = CtField.make("private int empno;",cc);
        CtField f2 = CtField.make("private String ename;",cc);
        cc.addField(f1);
        cc.addField(f2);

        //    
        CtMethod m1 = CtMethod.make("public int getEmpno(){return empno;}", cc);
        CtMethod m2 = CtMethod.make("public void setEmpno(){this.empno = empno;}", cc);
        cc.addMethod(m1);
        cc.addMethod(m2);

        //     
        CtConstructor constructor = new CtConstructor(new CtClass[]{CtClass.intType, pool.get("java.lang.String")},cc);
        constructor.setBody("{this.empno = empno; this.ename = ename;}");
        cc.addConstructor(constructor);

        cc.writeFile("g:/java/test");//                   
        System.out.println("   ，  ！");
    }
}

XJadを使用する逆コンパイル後に生成される.JAvaファイル

// Decompiled by Jad v1.5.8e2. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://kpdus.tripod.com/jad.html
// Decompiler options: packimports(3) fieldsfirst ansi space 
// Source File Name:   Emp.java

package com.test.bean;


public class Emp
{

    private int empno;
    private String ename;

    public int getEmpno()
    {
        return empno;
    }

    public void setEmpno()
    {
        empno = empno;
    }

    public Emp(int i, String s)
    {
        empno = empno;
        ename = ename;
    }
}

一、S 02 E 217_01バイトコード操作javaassistライブラリ紹介_API詳細

package com.test.javassist;

import java.lang.reflect.Method;
import java.util.Arrays;

import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtConstructor;
import javassist.CtField;
import javassist.CtMethod;
import javassist.CtNewMethod;
import javassist.Modifier;
/**
 *   javassist API
 */
public class Demo2 {
    public static void main(String[] args) throws Exception {
        test06();
    }
    /**
     *         
     * @throws Exception 
     */
    public static void test01() throws Exception{
        ClassPool pool = ClassPool.getDefault();
        CtClass cc = pool.get("com.test.javassist.Emp");//      

        byte[] bytes = cc.toBytecode();
        System.out.println(Arrays.toString(bytes));

        System.out.println(cc.getName());//    
        System.out.println(cc.getSimpleName());//      
        System.out.println(cc.getSuperclass());//    
        System.out.println(cc.getInterfaces());//    
    }
    /**
     *         
     */
    public static void test02() throws Exception{
        ClassPool pool = ClassPool.getDefault();
        CtClass cc = pool.get("com.test.javassist.Emp");//      
        //CtMethod m = CtNewMethod.make("public int add(int a,int b){return a+b;}", cc);
        //     ，  ：    ，   ，      ，CtClass  
        CtMethod m = new CtMethod(CtClass.intType, "add", 
                new CtClass[]{CtClass.intType,CtClass.intType}, cc);

        m.setModifiers(javassist.Modifier.PUBLIC);
        m.setBody("{System.out.println(\"           \");return $1+$2;}");

        cc.addMethod(m);

        //            
        Class clazz = cc.toClass();
        Object obj = clazz.newInstance();//  Emp     ，    Emp  
        Method method = clazz.getDeclaredMethod("add", int.class,int.class);
        Object result = method.invoke(obj, 200,300);
        System.out.println(result);
    }
    /**
     *             
     * @throws Exception 
     */
    public static void test03() throws Exception{
        ClassPool pool = ClassPool.getDefault();
        CtClass cc = pool.get("com.test.javassist.Emp");//      

        CtMethod cm = cc.getDeclaredMethod("sayHello", new CtClass[]{CtClass.intType});
        cm.insertBefore("System.out.println($1);System.out.println(\"start!!!\");");
        cm.insertAt(9, "int b=3;System.out.println(\"b=\"+b);");
        cm.insertAfter("System.out.println(\"end!!!\");");

        //            
        Class clazz = cc.toClass();
        Object obj = clazz.newInstance();//  Emp     ，    Emp  
        Method method = clazz.getDeclaredMethod("sayHello", int.class);
        method.invoke(obj, 300);
    }
    /**
     *         
     */
    public static void test04() throws Exception{
        ClassPool pool = ClassPool.getDefault();
        CtClass cc = pool.get("com.test.javassist.Emp");//      

        //CtField f1 = CtField.make("private int salary;", cc);
        //     
        CtField f1 = new CtField(CtClass.intType, "salary",cc);
        f1.setModifiers(Modifier.PRIVATE);
        cc.addField(f1);

        //cc.getDeclaredField("salary");//       
        //     
        cc.addMethod(CtNewMethod.getter("getSalary", f1));
        cc.addMethod(CtNewMethod.getter("setSalary", f1));

        //      ，  。。。
    }
    /**
     *      
     */
    public static void test05() throws Exception{
        ClassPool pool = ClassPool.getDefault();
        CtClass cc = pool.get("com.test.javassist.Emp");//      

        CtConstructor[] cs = cc.getConstructors();
        for (CtConstructor c : cs) {
            System.out.println(c.getLongName());
        }
    }
    /**
     *     
     */
    public static void test06() throws Exception{
        ClassPool pool = ClassPool.getDefault();
        CtClass cc = pool.get("com.test.javassist.Emp");//      

        Object[] all = cc.getAnnotations();
        Author a = (Author) all[0];
        String name = a.name();
        int year = a.year();
        System.out.println("name:" + name + ",year:" + year);
    }
}

javabean

package com.test.javassist;

@Author(name = "test",year= 2016)
public class Emp {
    private int empNo;
    private String empName;

    public Emp() {
    }
    public Emp(int empNo, String empName) {
        super();
        this.empNo = empNo;
        this.empName = empName;
    }

    public int getEmpNo() {
        return empNo;
    }
    public void setEmpNo(int empNo) {
        this.empNo = empNo;
    }
    public String getEmpName() {
        return empName;
    }
    public void setEmpName(String empName) {
        this.empName = empName;
    }

    public void sayHello(int a){
        System.out.println("sayHello," + a);
    }
}

注釈

package com.test.javassist;

public @interface Author {
    String name();
    int year();
}